The incidence of acute hepatitis C virus (HCV) coinfection has increased in recent years at the largest HIV clinic in Japan, with almost all cases occurring among men who have sex with men, according to a poster presented at the 53rd Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC 2013) this month in Denver. For those treated early with pegylated interferon plus ribavirin, the cure rate was high at 80%.

Since the early 2000s researcher have reported outbreaks of acute HCV infection among HIV positive gay and bisexual men, first in large cities in the U.K. and continental Europe, followed by Australia and the U.S. But there have been few reports on acute hepatitis C in East Asia.

Masahiro Ishikane from the National Center for Global Health and Medicine and colleagues conducted a retrospective cohort study looking at people with acute hepatitis C seen at the AIDS Clinical Center in Tokyo, the largest HIV clinic in Japan.

Acute hepatitis C was defined as alanine transaminase (ALT) elevation >100 IU/L accompanied by HCV antibody seroconversion. Acute hepatitis C is often asymptomatic and many people are not aware they are infected. People with HIV typically undergo frequent liver enzyme testing to monitor antiretroviral drug toxicity, however, and unexpected ALT rises may signal new HCV infection.

The researchers analyzed medical records from 34 patients diagnosed with acute hepatitis C between January 2001 and December 2012. All but 1 were men and the median age was 39 years.

Results

The overall incidence of acute HCV infection was 2.1 cases per 1000 person-years.

Incidence increased slightly over time, as shown by a higher rate in the past 5 years compared with the past 7 years (2.6 vs 1.5 per 1000 person-years, respectively).

All but 2 cases of acute HCV infection (94%) occurred among HIV positive men who have sex with men.

Most (82%) were on antiretroviral therapy with suppressed HIV viral load, and they had a median CD4 T-cell count of 366 cells/mm3-- indicating moderate immune suppression -- at the time of HCV diagnosis.

5 people (15%) reported a history of injection drug use, but the route of HCV transmission was classified as "undetermined" in all cases.

Most participants (82%) were asymptomatic and were diagnosed with HCV by chance at a routine clinic visit.

6 people experienced symptoms including fatigue (18%) and jaundice, or yellowing of the skin and eyes due to elevated bilirubin (6%).

68% had HCV genotype 1b, the most common type in Japan, while 25% had 2a or 2b, and 7% had 1a.

5 participants (15%) cleared HCV spontaneously without treatment; this group had significantly higher peak bilirubin levels than those who did not naturally clear the virus.

17 participants (50%) did not receive treatment and progressed to chronic HCV infection.

The remaining 12 patients (35%) started treatment with pegylated interferon plus ribavirin within 48 weeks of HCV diagnosis, with a median interval of 4 months between initial ALT elevation and starting therapy, and a median treatment duration of 45 weeks (range 11 to 72 weeks).

"Early treatment with [pegylated interferon plus ribavirin] should be considered for favorable response in HIV-infected patients with [acute hepatitis C]," the researchers concluded.

The HCV incidence rate in this study is similar to that seen among HIV positive gay men in the mostly European CASCADE cohort in 1990, before it increased by more than 10-fold in the late 2000s. Rates of 20 to more than 100 cases per 1000 person-years have also been seen in Amsterdam and in the Swiss HIV Cohort. However, a recent analysis of HIV positive MSM in the U.S. Multicenter AIDS Cohort Study found a rate of only about 5 per 1000 person-years during 2005-2011.

Studies of acute HCV infection among HIV positive gay men in the U.S., Europe, and Australia point to probable sexual transmission. HCV infection has been associated with various factors in different studies -- including fisting, anal intercourse, group sex, use of non-injected recreational drugs, and having other sexually transmitted infections -- but data have been inconsistent and the exact mechanism of sexual transmission is not yet fully understood.